This one of the best app that I use for charting .Whatapp messenger , a popular cross-platform text messaging alternative , lets you text and talk using data plan .But has about 800 millions user in the world and it avilable in ios, Android, blackberry and windows phone. Mostly massaging service required to create a account but whatsapp doesnot only you have give your mobile number they verify by text message.It doesnot required to search a friend .The contact number you saved from the other user , are automatically adds them as friend. It is also avilable now with upgrade feature voice calling and video calling which makes it more priority then other apps .